/*
    This file is part of the substandard lisp implementation of Standard Lisp
    Copyright (C) 2011 Nicky Nickell

    substandard lisp is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

function std_or(a, env) {
  var u = a[0];

  var last = null;
  for (var i = 0; i < u.length; i++) {
    last = u[i].evaluate(env);
    if (last != NIL) {
      return last;
    }
  }
  return NIL;
}

/*---
name: or
arity: 0
rest: true
ftype: FTYPE_FEXPR

argument-types:
  - CLASS_ANY
  
argument-names:
  - U

doc: |
  Returns the first of U which evaluates to non-NIL or NIL if none do.

tests: |
  (or T T) -> T
  (or NIL 1) -> 1
  (or NIL NIL NIL 2 3) -> 2
...*/
